/Engine/Source/Runtime/Engine/Classes/Engine/World.h
Called after GWorld has been set. Used to load, but not associate, all levels in the world in the Editor and at least create linkers in the game. Should only be called against GWorld::PersistentLevel's WorldSettings.
void LoadSecondaryLevels ( bool bForce, [TSet](API\Runtime\Core\Containers\TSet)< [FName](API\Runtime\Core\UObject\FName) > * FilenamesToSkip )